Courtesy of landismom, I've been introduced to Good Reads, a social book rating service. So if Library Thing isn't taking up all your online book cataloguing-and-commenting energy, check this one out. I've never delved into myspace or facebook; I've been fascinated to see how easily the site enables me to, say, use my gmail address book to invite people to be friends (which I did without really realizing I was doing it--Politica tells me she got an invite and I didn't realize she was in my gmail address book), and then how some friends-of-friends are now contacting me. This commentary marks me as hopelessly behind the times, I realize.
I'm not sure how much I'll use it, and not yet sure how I think it compares to Library Thing (which is set up to be more of a catalogue, not a rating service). But worth checking out, I think.